How to fix Buick GL8 acceleration problem?

I repaired a Buick GL8 that could not accelerate while driving last week. According to the car owner, the Buick was equipped with a 3.0 engine and a 4T65E automatic transmission, with 120,000 km on it.

The owner told me that it could not speed up when he was driving the car, which made it extremely difficult to climb up a slope. Every time he came to an upslope, he had to press the accelerator pedal all the way to push the car up the slope.

After I received the car, I first started to diagnose the problem by using GM Tech 2 diagnostic tool. Test result from the OBD2 tool showed that ther automatic transmission of the car was broken, so that the vehicle could not go faster than 130km/h.

Then I troubleshot the automatic transmission control system with the GM Tech 2 again, and pulled two error codes: P0756 and P0758. The former means 2-3 shift solenoid B circuit fault, while the latter means 2-3 shift solenoid B electrical fault.

After troubshooting the problem, I went a test drive and checked the data flow while driving. Then I pulled out the plug connecting the automative transmission, and tested the resistance of 2-3 shift solenoid valve, which turned out to be infinite. When I tested the resistance with other solenoid valves, their numbers were normal.


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